The present invention provides improvements in changeable signs. The inventor of this application, Fred M. Black, is the inventor of U.S. Pat. No. 4,761,905 entitled "Scanned Electromechanical Display" and U.S. Pat. No. 4,912,442 entitled "Scanned Electromechanical Alphanumeric Display Apparatus". Additionally, Fred M. Black is a co-inventor of U.S. Pat. No. 5,412,891 entitled "Changeable Sign". The disclosures of these patents are hereby incorporated herein by reference. The '905 and '442 patents provide a description of certain designs of the prior art in the field of the present invention. Additional improvements are disclosed in application Ser. No. 08/761,125, filed Dec. 6, 1996, and application Ser. No. 08/831,071, filed Apr. 1, 1997, both of which are incorporated herein by reference.
The cited patents and applications disclose sign elements which can display alphanumeric or graphical information through the selective arrangement of individual display elements. The display elements are rotatably mounted elements that have multiple display faces, only one of which is noticeable to an observer at a time. The overall pattern of pixel display faces makes up an alphanumeric or graphical indicia of the sign. The present invention has these notions in common, but provides improved design features to create a superior product.
The previous designs require the use of an external light source during low lighting conditions to provide illumination of the display face. Although this arrangement performs adequately, it requires special mounting hardware for mounting the external light source. In many instances, the displays are mounted in small, isolated positions that do not have space or available positions to mount the external lighting.
There is a need for a display apparatus made up of individually illuminated pixels. Present displays provide for internal illumination of the entire display face or for entire columns or rows of pixels. The individual pixels can not be either "on" in which they are internally illuminated or "off" having no internal illumination. There is no ability for the individual pixels to be either "on" or "off" in correlation to the display being presented to the viewer.
Thus, there exists a need for a display apparatus having individually illuminated display pixels which together form a display front for showing alphanumeric or graphical indicia.